Book Image

Learning OpenCV 3 Application Development

By : Samyak Datta
Book Image

Learning OpenCV 3 Application Development

By: Samyak Datta

Overview of this book

Computer vision and machine learning concepts are frequently used in practical computer vision based projects. If you’re a novice, this book provides the steps to build and deploy an end-to-end application in the domain of computer vision using OpenCV/C++. At the outset, we explain how to install OpenCV and demonstrate how to run some simple programs. You will start with images (the building blocks of image processing applications), and see how they are stored and processed by OpenCV. You’ll get comfortable with OpenCV-specific jargon (Mat Point, Scalar, and more), and get to know how to traverse images and perform basic pixel-wise operations. Building upon this, we introduce slightly more advanced image processing concepts such as filtering, thresholding, and edge detection. In the latter parts, the book touches upon more complex and ubiquitous concepts such as face detection (using Haar cascade classifiers), interest point detection algorithms, and feature descriptors. You will now begin to appreciate the true power of the library in how it reduces mathematically non-trivial algorithms to a single line of code! The concluding sections touch upon OpenCV’s Machine Learning module. You will witness not only how OpenCV helps you pre-process and extract features from images that are relevant to the problems you are trying to solve, but also how to use Machine Learning algorithms that work on these features to make intelligent predictions from visual data!
Table of Contents (16 chapters)
Learning OpenCV 3 Application Development
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface

Image cropping -- basics


For now, we have rotated each face image so that the eyes are horizontally aligned. In this section, we will introduce the next step in the alignment pipeline. We are going to talk about an operation that is very common and ubiquitous with images-cropping. Each one of you, at some point in time, must have used the image cropping feature in one or the other image processing software (Paint, Photoshop, and so on). We are going to show how cropping works in OpenCV.

The cropping operation that we define here is for rectangular image regions. Before we dive into the details, let's try to think for ourselves how such an operation might be defined within the framework of whatever we know about OpenCV. Let's say that you are given an image that you want to crop. If you are using your favorite GUI-based cropping tool, how would you proceed? The natural thing to do would be to take the mouse pointer and place it at one of the points near the region that you want to crop. After...